DWC question.

I am currently doing my first grow using 51/2 gallon bubble buckets, im finding that when the buckets go down to about half full then the ph of the solution suddenly drops.

Im just wandering if this could be a problem or if its normal? Its happened 3-4 times now and when i fill them back up there ok until they reach about half empty.

All i can think is that the plants are taking up more water than nuites so as the buckets empty the nuites lower the ph of the solution?

Any ideas would be greatly appreciated.

Yeah, I have the same issue, but I've had great success with my bubblers. Just give water then and you'll be fine. How many buckets do you have, because at the end of your grow you will be adding over a gallon per bucket per day. The roots will take up so much space there won't be a lot of room for water. I would suggest getting a controller for about $50-60 that will hold 20 gallons at least. Look up Texas Controller online and then look for cheaper off brand stuff. Also, if your plant is taking up more water than nutes, you can do one of two things. I would suggest lowering your nutes until your plants take up the same ratio of water and nutes. That's the advice directly from our 20+ year hydro store rep in my city and it's worked much easier for me. Or you could fill your buckets with your normal PPM then fill the controller with 1/4 to 1/2 strength nutes.
My I offer unsolicited advice on Bubblers? I've found that the salt-based hydro solutions tend to crystalize and clog the air line when the water gets extremely low, and the hydro guy did say it will give a harsher taste to my "strawberries". He highly suggested not using his own product but use the organic based Botainicare grow and bloom because it won't crystalize when the water gets low like that and it's gentler on the roots if it gets PPM out of wack.
I know I don't have a lot of experience posting on here, but I've been using my bubblers for a few years, and it just keeps getting better. I love bubblers because you can change stuff around really easy, even move plants mid-grow to a different system setup.

Yeah, if the buckets are linked, you need to have a large reservoir with a 'feeder' bucket hooked up to it via a float valve. This will keep your water level consistent and your ph in check.

Thanks for the advice guys. The buckets aren't linked but I will keep them well topped up and ill also lower the ppm a little